A vehicle may include an engine that may be automatically stopped and started to conserve fuel. The engine may be stopped via a controller in response to vehicle operating conditions without receiving a specific request to stop the engine from a human driver or occupant of the vehicle. For example, the engine may be automatically stopped in response to driver demand torque being less than a threshold torque and a human driver applying a brake pedal. The engine may be automatically restarted after it has been automatically stopped in response to a driver demand torque that is greater than a threshold torque. However, if an attempt is made to automatically restart the engine with a battery that is degraded or partially degraded, the engine may fail to restart. The vehicle's human driver may attempt to manually restart the engine, but the manual attempts to restart the engine are also likely to be futile because of the degraded state of the battery. The vehicle's human driver may also succeed in restarting the engine by jump starting the engine using a second battery. Nevertheless, if the engine is subsequently automatically stopped, the engine may once again fail to restart due to battery degradation.
The inventor herein has recognized the above-mentioned issues and has developed a powertrain operating method, comprising: increasing loads of vehicle electrical accessories via a controller during deceleration fuel shut off in response to an indication that the battery has been replaced or boosted; and inhibiting automatic engine stopping via the controller in response to the voltage of the battery decreasing more than the threshold amount.
By applying an electrical load to a battery during deceleration fuel shut off of an engine, it may be possible to assess the presence or absence of battery degradation so that automatic engine stopping may be allowed or prohibited. In one example, output of an alternator is reduced to zero while one or more electrical loads are applied to the battery while the engine is rotating and not combusting fuel. Operation of the engine in this way prevents engine misfires while allowing the battery to be drained of charge so that battery health may be evaluated without interference from electrical output of the alternator. In addition, since the engine is already rotating, the engine does not have to be rotated via an electric machine to restart the engine.
The present description may provide several advantages. In particular, the approach may allow for diagnosing a battery in a way that reduces the possibility of engine no start conditions. Further, the approach allows or prevents automatic engine stopping based on state of the battery so as to reduce the possibility of engine no starts. Further still, the approach diagnoses a battery in a way that allows an engine to operate without misfires.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.